How to efficiently utilize the second crop of Oriental lily flowers
Oriental lily bulbs are generally grown for only one crop abroad, then dug up and discarded. Based on China's national conditions, Chinese lily growers have developed a reuse technique for Oriental lily bulbs, which is now applied in many places. However, because the second-crop flowers produced by reusing Oriental lily bulbs are mostly harvested and marketed from June to August, when the price of lily cut flowers@#@136@#@is relatively low, the economic benefit is limited. In the past two years, the Gansu Provincial Flower Engineering Technology Research Center, in cooperation with Gansu Lintao County Meilan Flower Company and the Lintao County Seed Farm, has explored a new model for the efficient second-crop utilization of Oriental lily bulbs, delaying the marketing period of the second-crop flowers to October-November, thereby raising the selling price and greatly improving the economic benefit. This new model is deeply welcomed by local lily growers and has considerable value for promotion and application. Its production process and technical key points are introduced as follows:
Production process
After flower harvest in January, bulbs are grown on for 4 weeks -> natural low-temperature treatment in place for 6-8 weeks -> bulbs dug in early April -> bulb sorting and disinfection -> frozen storage of bulbs for 3-4 months -> planting in July and August for cut flower cultivation -> flower harvest in October-November.
Cold treatment of bulbs
At present, the Oriental lily cultivars used in this model are 'Siberia' and 'Acapulco', and the greenhouse used is a solar greenhouse. Post-harvest bulb growing is carried out according to the general second-crop utilization technique, that is, when harvesting the flowers, about 25cm of the stem base is left, appropriate irrigation is given, and the air temperature in the greenhouse is kept at 18°C-25°C. After 4 weeks, the nutrients of the stems, leaves and stem roots are transferred into the bulbs, rejuvenating them.
After bulb growing is completed, cold treatment of the bulbs is carried out. The method is to use natural low temperature for the treatment. Specifically, the solar greenhouse is ventilated more intensively, with the vents opened to the maximum and not closed day or night; during the day it is shaded, with straw curtains or thermal insulation quilts and other external insulation covering materials lowered, and at night they are rolled up. In this way, the air temperature in the solar greenhouse drops to 0°C-3°C, and the substrate temperature is 3°C-5°C. If the temperature in the greenhouse drops too much, the vents can be appropriately closed, or the curtain-covering time adjusted, to maintain the above temperatures. Under these low-temperature conditions, after 6-8 weeks, the bulb dormancy can generally be broken. The cold treatment can be ended as soon as the bulbs begin to sprout. If individual bulbs sprout too early, the young shoots must not exceed 1cm in length, otherwise the young shoots are easily damaged and harmed by freezing during subsequent handling and frozen storage.
Harvesting, cleaning, disinfection and boxing of bulbs
Bulbs are harvested manually with a shovel, taking care not to damage the scales so as to reduce wound infection and prevent rot; at the same time, care should be taken to keep the basal roots of the bulbs intact. When digging, the digging should start 15cm away from the bulbs, and the digging depth is 20cm. After the bulbs are dug out, the soil on the bulbs is removed, and the withered stem axis is cut off. Then the bulbs are gathered and gently placed into boxes.
Bulb cleaning. Bulbs transported to the cleaning and disinfection workshop should be cleaned as soon as possible. The bulbs are placed in bulb boxes and rinsed with clean water, not only to remove the soil and debris attached to the outside of the bulbs, but also to remove soil and other debris from the gaps between the scales and among the basal roots.
Bulb disinfection. Lily bulbs are tunicless bulbs and are very susceptible to infection by pathogens, which leads to rot and loss of value. Common diseases during bulb storage mainly include bulb soft rot, penicillium rot and brown scale disease. To prevent these diseases, in addition to avoiding damage to the bulbs as much as possible during digging and post-harvest handling to reduce pathogen invasion, disinfection of the bulbs before entering the cold storage is particularly important. For disinfection, the cleaned bulbs, together with the boxes, are immersed in a disinfection tank for 30 minutes. The disinfectant solution is generally 50% carbendazim wettable powder at 600 times dilution and iprodione at 800 times dilution; 80 times formalin aqueous solution can also be used, or 75% chlorothalonil wettable powder at 500 times dilution. After the bulb boxes are taken out of the disinfectant solution, they are rinsed clean with clear water, stacked, and the water on the surface of the bulbs is drained, in preparation for boxing and storage.
Bulb boxing. Rectangular plastic baskets are usually used, with peat as the filling substrate, and the substrate needs to be disinfected in advance. The substrate requires suitable moisture, judged by no water being squeezed out when pinched by hand, that is, a moisture content of 50%-70%. This keeps the bulbs in a constantly moist environment and prevents dehydration, while too much moisture easily causes the bulbs to rot in the boxes.
When boxing, first line the bottom of the bulb box with plastic film, then spread a layer of filling substrate about 3cm thick on the film, place a layer of bulbs and then sprinkle a layer of substrate, alternating in this way until the box is full, and seal the top of the box tightly with plastic film. The plastic film should be perforated for ventilation, generally 14-18 holes per square meter. A label is affixed to the box, clearly stating the cultivar, quantity, bulb size and storage date, etc.
Frozen storage of bulbs
Selection of cold storage. Frozen storage of lily bulbs requires the use of a professional bulb cold treatment store. This kind of cold storage must meet the following conditions: (1) the cold storage wall must have an insulation level of 0.3W/(m2 k); (2) the cold storage must have a refrigeration capacity of 40-60W per cubic meter of refrigerated volume; (3) an automatic slow ventilation device must be installed; (4) there must be a certain air circulation; (5) circulating fans must be installed to ensure a uniform temperature inside the storage, with a fluctuation range of less than 0.5°C.
Frozen storage technique. After the bulb boxes are put into storage, they are stacked layer by layer in the cold storage. The bottommost boxes must not bear too much weight, and the bottom of the bottommost boxes must not be directly against the ground; when placing them, they should first be raised with wooden strips. Gaps should also be left between the stacked bulb boxes and between the bulb boxes and the top of the cold storage, and walkways should be left in the middle for frequent inspection.
Freezing time. The freezing period is generally about 3-4 months. During this period the bulbs do not suffer freeze damage, the young shoots basically stop elongating, and in 4 months they elongate by no more than 1cm. Bulbs stored frozen in this way can emerge, grow and flower normally after being taken out of storage and planted.
After the bulbs that have finished freezing are taken out of the storage, they are first placed at 10°C-15°C for a warming transition, and must not be exposed to sunlight, to avoid a decline in quality; after 12 hours they must be planted immediately.
Cut flower cultivation
The planting period for bulbs that have undergone the above treatments is generally July-August, and the flower harvest period is October-November. The planting method and field management are basically carried out according to the practices for first-crop cut flower cultivation, the only difference being appropriately increasing the application rates of base fertilizer and topdressing to ensure the nutritional supply for plant growth and development, ultimately producing high-quality cut flowers.